Jim,
Maybe if I run
through how we set it up you might get some ideas. Before I start this is how
our ERP is designed and would certainly be overkill for a simple shopping
cart. It will hopefully give you some ideas on how to build a robust
discounting system though.
First off we broke
discounts into two types.
1.Whole of order –
applies to order total
2.Product line –
applies to each product only
For whole of order
discounts our process runs like this.
Our system uses
events to handle orders as they have a distinct lifecycle ie, open, amend,
processDiscount, processInvoice, etc. We have a manager object which handles
order objects but also retrieves discount and tax types. After a user has
completed an order we have an order object sitting in the manager. To apply a
discount we trigger a discount event on the order as follows:
-
shoppingCartManager.getDiscountType() – Returns a discount object based
on myOrder.discountContext (property of order). This is where you could supply
a coupon number.
-
shoppingCartManager.myOrder.processDiscountEvent(discountObject) – creates a
discount event in the order object with discount object
-
myOrder.discountEvent.discount.calculateDiscountedPrice(totalPrice) – this is
a call to the discount object to calculate and return the discount on the
order total.
The beauty of this is
that we can apply multiple discounts to an order total by stacking them in
discountEvent.
Now for product lines
we don’t calculate discounts on an order line. Instead we use product/package
pricing. Meaning we don’t associate discounts with an orderline but with a
product itself. So here are the steps with this.
- Get precondition
which could be customer, order quantity, coupon number.
-
orderline[n].product.getPrice(preconditions) – on each order line we have a
product object which is responsible for it’s own pricing. We use rule sets and
catalogues to filter prices on preconditions passed in. It would take me a day
to fully explain what goes on here but you could build some pretty simple
rules here like ‘buy 6 get 1 free’. Even with a simple application you can
quickly build up a set of rules. The point here is that your rule is tied to
the product rather than the order.
Bottom line is to
correctly define your discount type before you start. Does it apply to the
whole order or a product? What are the conditions that must be met before the
discount can be given? If there is more than one discount in what order are
they applied?
This is pretty full
on for a simple shopping cart hey? Anyway, food for thought
J
Angus
-----Original
Message-----
From:
[EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim McMullen
Sent: Thursday, 24 March 2005 12:58
AM
To:
[email protected]
Subject:
[CFCDev] Help with OO Model for Shopping Cart
I have a typical CFC-based
shopping cart (ShoppingCart object holds a struct of CartItem objects).
This works well and I have no real problem with it.
However, I now need to implement a
pretty robust coupon/discount functionality into the app, and I can't
seem to figure out how to do it. I need to allow for four types of coupons:
(1) Whole order coupon (NN% off
entire order)
(2) Single item coupon (NN% off
this item)
(3) Multiple item coupon (buy one
(or two), get the 2nd (or third) NN% off)
(4) Free item coupon (buy this
item, get a free toaster)
I think I can figure out how
to model a single coupon type, but as I'm an OOP newb, figuring out
how to model and implement the whole range has got my head
spinning.
Can anyone point me in the right
direction?
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